(1) Field of the Invention
This invention relates to electronic computers and data processing systems and more particularly to apparatus for measuring testing, analyzing or monitoring such systems in operation.
(2) Description of the Prior Art
Some prior devices have dealt with the analysis of digital systems in general, but because their target of applications was so wide these devices have been rather complex internally, somewhat difficult to operate, fairly bulky, and not quickly and inexpensively adaptable to a given computer. U.S. Pat. No. 4,040,625 for "Logic State Analyzer" to Morrill, Jr. et al is an example of such prior art devices.
Another prior art device is shown in U.S. Pat. No. 3,805,255 for "Scanning Light Emitting Diode Display of Digital Information" to Baker. This device employs Light Emitting Diodes (LED's) to indicate the logic state of each bit of a sequence of two input streams of binary bits and has the further capability of displaying the results of selected boolean operations on corresponding bits of the input streams of bits. Such a device does not provide a display of signal flow within a computer and no means is disclosed for adapting such a device to analysis of the binary bit signal streams existing in an operating computer system.
Other prior devices have dealt specifically with the analysis of computer systems but have, as a result of using one axis for a time based function, required an expensive, power consuming, large, high-resolution display. Also, no provision for convenient adaption to varying computers was included. U.S. Pat. No. 3,522,597 for "Execution Plotter" to Murphy and U.S. Pat. No. 3,098,219 for "Monitoring Arrangement For Program-Controlled Electronic Computers or Similar Systems" to Voight et al are examples of such prior art devices.
U.S. Pat. No. 3,829,841 for "Computer Monitoring Device" to Steinberg is an example of prior art devices used to provide a graphic display of computer execution of programmed instructions. Such devices are useful as aids in the analysis and error identification in the flow of program instructions in the computer. These devices, however, are very complex and expensive and do not permit selective analysis of specific signals flowing on the signal buses of the computing device under analysis.
Yet other prior devices such as Emulators have been useful in the analysis of computer systems but provide information in alphanumeric format allowing detailed and accurate analysis of precisely requested data, but not allowing the intuitiveness and speed of a graphic display.
In general, a cathode ray tube (CRT) with its size, fragility, power consumption, high voltage, and drive circuits is used in the prior art devices that have graphic displays. In comparison with previous devices, the disclosed apparatus is economically manufacturable, simple to use, portable, readily adaptable to different computers, and presents information in a way that alone is very useful and when used as a supplement to existing tools provides a fresh perspective as an aid to solving difficult problems.